1. Field of the Invention
The present invention relates to an apparatus for detecting the rotational angular positions of the crankshaft of an engine in an automobile or the like, particularly a rotation detecting apparatus capable of detecting the reference angular position and incremental rotational positions of a rotating object such as the crank shaft of an engine without any delay irrespective of its rotational speed. More particularly, the invention relates to a capacity type rotation detecting apparatus in which the transmission of signals is effected by means of the capacitance between the electrodes arranged opposite to one another.
2. Description of the Prior Art
The apparatuses heretofore known for detecting the rotation of the crankshaft of an automobile engine include those in which a magnetic member having a coil would thereon is positioned opposite to a rotational member and an alternating electromotive force is induced in the coil in response to the magnetic flux variations caused by the projections on the rotational member, thereby detecting the rotation of the rotational member.
However, this type of apparatus is disadvantaneous in that the alternating electromotive force induced in the coil is affected by the magnetic flux variations, that is, by the rotational speeds of the rotational member and thus, if the rotational speed of the rotational member is low, practically no alternating electromotive force is induced in the coil, making it impossible to detect the rotation of the rotational member.
Another disadvantage is that where the detection of incremental rotational angle signals (i.e., rotational position signals) and reference angular position signals is required, respective corresponding projections must be separately arranged on the rotational member and detecting means must be provided at two places making the construction complicated.